The present invention relates to fish processing machinery and, more particularly, to machinery for eviscerating and removing a dorsal fin of fish.
Although the present invention may have applicability to processing other types of fish, for concreteness of description, the invention is illustrated and described in an embodiment especially suited to processing channel catfish (Ictalurus Punctatus).
Conventional catfish processing includes removing the head, slitting the belly cavity, cleaning the viscera from the belly cavity, and skinning the cleaned fish for market. Such conventional processing, besides being extremely labor intensive, fails to produce a cleaned fish having all of the attributes desired by consumers.
In the most primitive practice, the catfish first are immobilized by electric shock to avoid worker injury from the sharp dorsal and pectoral spikes. Next, their heads are removed using a bandsaw and their belly cavities are manually slit with a knife. The viscera are drawn from the body cavity with the help of a vacuum hose. Finally, the skin is removed by a hand-fed conventional mechanical skinner.
In a more modern process, the head-removal and belly-slitting procedures are done with conventional automated machinery to deliver beheaded and belly-slit fish to the remaining operations.
The eviscerating operation using a vacuum hose requires substantial human effort to complete. Parts of catfish viscera are extremely tough and well attached to the remainder of the fish. For example, a swim bladder in the forward part of the beheaded fish is tough, resilient, and difficult to remove. In addition, a portion of the intestine remains firmly attached to the anal vent at one side or the other of the belly slit. To remove these items, the worker must clamp the item to the vacuum hose nozzle with one hand while holding the remainder of the fish with the other. Such manual processes substantially slow the eviscerating operation and contribute to worker fatigue.
Even when completely eviscerated, catfish cleaned by the above process have certain properties which limit their sales appeal. For example, the belly cavity of a catfish is lined with a dark layer which many fish buyers find unattractive or unappetizing. In addition, an undesirable amount of blood and debris conventionally remain in the body cavity, especially in the vicinity of the spine and near the rear end of the body cavity.
The pectoral fins of a catfish may be removed as part of beheading. The dorsal fin presents several difficult problems. Dorsal-fin removal is important since the dorsal fin contains a stiff, sharp spike whose presence in the dressed fish not only reduces the attractiveness of the product but also presents a safety problem. The leading edge of the dorsal fin is attached to the back of the catfish by a triangular bone plate which must be removed along with the fin. To maintain the yield of flesh from the dressed fish excessively deep cuts to remove the dorsal fin and triangular bone plate should be avoided.